In recent years, three-dimensional displays (3-D displays) are being provided for car navigation, portable navigation, navigation for portable telephones, and the like. Various improvements have been made to ease identification of the position of a viewer, the direction of motion, and the like.
In the case of 3-D displays, the use of photos for portions of the display requires time and labor for preparation. In addition to the high expense of data creation, there is greater data volume, increased use of storage memory, and increased processing time, and greater data volume, increased use of storage memory, and increased processing time, and therefore, the use of photos is usually not desired in the display. In the cost-competitive field of navigation systems, there is widespread use of computer graphic (CG) image data to allow simple and inexpensive processing.
With CG images, innovations have been made to provide as much photorealism as possible, and these innovations are applied not only to three-dimensional objects for architectural objects such as buildings but also to sign objects such as displays. As a result, these sign objects are in some cases complex, resulting in the overall image giving an impression different from that of the actual location. Alternatively, there may be too fine, complex overlapping of images, which reduce the ease of viewing.
In the present invention, sign objects refer to objects for advertisements, building names, street names, store names, and the like, as well as objects of signs for textures, pictures, colors, designs and the like for traffic signs and the like, either singly or in combination. Three-dimensional objects refer to objects in which sign objects have been removed from a 3-D display screen, e.g., buildings, bridges, streets, and rivers. Various improvements in 3-D screen displays have been attempted. For example, Japanese Laid-Open Patent Publication Number 2001-34160 (Patent Document 1) describes an improvement in the display of sign objects to avoid overlapping displays in these sign objects.